1. Field of the Invention
The present invention generally relates to a pixel array, and more particularly, to a pixel array formed on a flexible substrate.
2. Description of Related Art
With recent advancement in video technology, different kinds of display devices have been applied to display screens of consumer electronic products such as cell phones, notebook computers, digital cameras and personal digital assistants (PAD) in a great quantity. Having the advantages of light weight, compact size and lower power consumption, LCDs (Liquid Crystal Display) and OLEDs (Organic Electro-Luminescence Display) have become the mainstream in the market. No matter an LCD or an OLED, the fabrication process of both displays comprises the step of forming a pixel array on a substrate by using a semiconductor process. The image displayed on the display devices is generated by adjusting the colour of each pixel of the pixel array. However, in order to make the electronic devices portable (as designed in a foldable structure), the pixel array is formed on a flexible substrate so that the displays will have flexibility to be assembled with the electronic products.
FIG. 1A is a partial vertical view showing a conventional pixel array. Please refer to FIG. 1A, the pixel array 100 formed on a flexible substrate 50 is composed of a plurality of pixels 100a arranged in a matrix. The pixel array 100 comprises a plurality of thin film transistors 110, a plurality of scan lines 120, a plurality of data lines 130 and a plurality of pixel electrodes 140. Each thin film transistor 110 is electrically connected to the corresponding scan line 120, data line 130 and pixel electrode 140; and the thin film transistor 110 is turned on or turned off according to the scan signals transmitted from the scan line 120. When the thin film transistor 110 is turned on, the pixel electrode 140 receives the data signal transmitted from the data line 130 to make the corresponding pixel 100a adjust its colour.
FIG. 1B is a schematic cross-sectional view of FIG. 1A taken along line A-A′. FIG. 1C is a schematic view showing the flexible substrate of FIG. 1B after it is warped. Please refer to FIGS. 1A, 1B and 1C. In general, the method of forming the scan lines 120 comprises the following steps. First, a metal layer is deposited on the flexible substrate 50, and then the metal layer is patterned by using a photolithography process to form the scan lines 120. However, during the process of warping the flexible substrate 50, the strain stress or tensile stress generated from the flexible substrate 50 would damage the pixel array 100 disposed thereon, particular the longer lines, such as the scan lines 120, and a break 120a occurs in the scan line 120 as shown in FIG. 1C.
Besides, a dielectric layer 150 covers the scan lines 120 as shown in FIGS. 1B and 1C. Similarly, when the strain stress or tensile stress generated from the flexible substrate 50 is applied to the large-sized dielectric layer 150, a crack 150a would easily occur. The cracks of the dielectric layer 150 may cause the problem of short circuit and result in defects of the pixel array 100.
The above-mentioned problems may also occur in the data lines, other lines or dielectric layers of the pixel array. Therefore, it is important to prevent the lines or film layers formed on the flexible substrate of the pixel array from cracking.